What is supply air?

Supply air refers to the air that has been conditioned—meaning it has been heated, cooled, or otherwise treated to achieve a desired temperature and humidity level—and is delivered to the spaces within a building where occupants are present. This air plays a crucial role in maintaining indoor air quality and comfort, as it directly affects the environmental conditions that people experience.

Conditioning the air involves filtering and adjusting its temperature to ensure that it meets the demands of the occupied space. This process is vital for effective heating, ventilation, and air conditioning (HVAC) systems, which aim to create a comfortable atmosphere while also ensuring fresh air circulation and promoting health standards.

In contrast, the other choices involve different air types that do not define supply air. Air being pulled in from outside refers to intake air, stale air exiting the building describes exhaust air, and air being returned from occupied spaces pertains to return air. Each of these plays a unique role within the HVAC system but does not reflect the characteristics of supply air.